DRYING FIREWOOD MOTHER NATURE HAS BEEN DRYING FIREWOOD for CENTURIES —Make That a Millennia

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DRYING FIREWOOD MOTHER NATURE HAS BEEN DRYING FIREWOOD FOR CENTURIES —make that a millennia. Unlike years past, we have been splitting firewood using bigger, industrial equipment for a few decades. In the last 5 to 10 years, we have also seen an increase in the use of PA ST, firewood kilns, though in the not-so-distant past, kiln drying firewood was unheard of. But the firewood industry is changing due to regulations for eliminating bugs and the subsequent , customer demand for kiln-dried firewood. PRESENT hat is kiln-dried firewood? What is stand that heat-treating firewood does not neces - seasoned firewood? These are sarily mean it is dry or that it will not mold later. questions with a variety of On the contrary, experience in heat-treating pal - answers. I am unaware of any rec - lets indicates that new pallets may be more likely ognized standard other than sever - to mold after they have been heat-treated. Is this WDal websites that suggest 20% moisture content true for firewood as well? The USDA initially (MC) when listing the Btu value of one cord of fire - required a temperature of 160°F inside the firewood , wood. While there really is no official or legal standard for 75 minutes. Currently this is reduced to 140°F for FUT UR E pertaining to dried firewood, I will use the 20% mois - 60 minutes; however, some states still hold to the old ture content as our benchmark in this article. In a simi - 160°F standard. When selecting a firewood kiln, it lar vein, it is not possible to truly qualify the actual may be wise to ensure it has the ability to meet the moisture content of “fresh split” firewood—for obvious 160°F for 75 minutes standard—unless you firmly AND GETTING STARTED reasons. Still it seems that most agree that the moisture believe the government will not revert to the higher content of “fresh split”—i.e., freshly logged and imme - standard at some future date. by Niels Jorgensen diately split—is often 60% or more. Kiln-dried firewood may be the coming standard for There are countless methods for testing the mois - bundles (usually 3/4 cubic feet) and other unit-load ture content of firewood. Here are a few: measuring delivery of firewood. Unit load means bundles, racks, the side using 1/4-inch-deep pins, measuring the end large bags, palletized/stacked, or other non-bulk deliv - using 1/4-inch pins, or splitting the wood in half and eries. There seems little doubt that firewood bundles testing the inside. It is our opinion that—scientifically have led the way, as it is surprising how far a firewood speaking—the best, though cumbersome, way of bundle is transported from the producer to the con - determining moisture content is to use the oven sumer. A few examples: Firewood produced in Florida method (for more information on this, see www.kiln- ends up in North Carolina; firewood from Virginia and direct.com/understandfirewoodmc). The most practical Tennessee is shipped to Florida; Wisconsin firewood is approach is splitting the piece such that a core mois - transported to Colorado; and producers in northern ture content reading can be made. It is my observation Maine send firewood to Philadelphia retailers. This that drying firewood down to an average of 20% MC magazine has run many articles about the dangers of most likely indicates the firewood is 14% to 17% MC transporting disease- or insect-infected firewood for on the outside surface and 25% to 30% MC in the cen - long distances. The wide-ranging transportation is ter/core. mentioned here in terms of commerce, but there are obvious cautions in terms of insects and diseases that What Is Heat-treated Firewood? come into play here as well (see Table 1). It is firewood that has been heated to a certain inter - Contrary to what some may think, kiln drying is not nal temperature for the purpose of killing a pest, such all about making firewood more expensive. Table 1 as an insect or bacteria. It is very important to under - compares fresh-split and kiln-dried firewood as it

4 • Sawmill & Woodlot Dec 2014/Jan 2015 • 2 for the future and (called supply temperature), but exit temperature that is the con - and steam temperatures are esti - SPECIES Btu/cord of Btu/cord Increase in t a k e advantage of a the more important number is exit - cern, as that is the temperature mated. Heat-up time will vary Fresh Split at 20% MC Btu/Cord changing market - ing temperature (called exit tem - known to be the lowest point of greatly depending on the size of place driven by perature). The exit temperature is reference in terms of how quickly the heat system and start tempera - Ash, white 16.5 million Btu 23.6 million Btu 7.1 million Btu increasing regulatory the one you should consider most the slowest firewood is drying. ture of the firewood. Hackberry 14.6 million Btu 20.8 million Btu 6.2 million Btu oversight? carefully when you review Table 2 . Drying times in hours and days Table 3 compares some generic Maple, red 13.1 million Btu 18.7 million Btu 5.6 million Btu Just to clarify, supply temperature are based on exit temperature in heating systems often found on fire - Oak, red 16.8 million Btu 24.0 million Btu 7.2 million Btu Drying is not the real concern in drying Table 2, plus actual experience wood kilns. Basically, it is difficult to Average increase in Btu per cord from fresh split to 20% MC: 6.5 million Btu Firewood and heat-treating firewood. It is the with installed kilns. The hot water get below 36 hours in total cycle It takes a lot more to Source: www.engineeringtoolbox.com/wood-combustion-heat-d_372.html dry firewood than These are generic numbers and will vary greatly with actual data due to differences in HEATING AVG. HEAT MAX SUPPLY EST. EXIT HOURS ESTIMATED most people imag - fresh-split MC% due to season, region, etc., and the 20% average moisture content is SYSTEM SURFACE TEMP. TEMP TEMP DAYS probably lower than most seasoned and kiln-dried firewood. ine. Here’s how it works: Hot water 190° F 170° F 140° F 120–200 hrs.+ 5–10 days Drying happens –160° F heat-up time Table 1. Increased Btu Value of Kiln-dried Firewood (20% MC). mostly through vapor Low-pressure steam 250° F 220° F–230° F 180° F 50–85 hrs. + coming out of the –200° F heat-up time 2.5–4 days relates to the increase in burnable al regulations, mold prevention, end, but why? Look at the end of High-pressure steam 300° F 260° F * 220° F 30 hrs. + Btus. The average increase in heat - customer or retailer demand, kiln- wet firewood in a fireplace when the heat-up time 1.5–2 days ing value is 30% to 40%, so techni - dried and heat-treated firewood water is bubbling out. The air in the Direct gas heating NA direct 260° F * 220° F 30 hrs. + cally the firewood should be worth emerges as the industry standard, kiln chamber transfers heat to the gas flame heat-up time 1.5–2 days 30% to 40% more, which is often how can those in the firewood firewood, it evaporates water, and Air-to-air heat 600° F–800° F 260° F * 220° F 30 hrs. + 1.5–2 days the case. It is also worth noting that industry prepare for such a signifi - then this same air transports the exchanger from heat-up time dry firewood weighs less per cord, cant shift of product? water vapor away. This is why good wood waste firebox which means you can ship more per Nature’s pathogens (emerald ash airflow is so critical in a firewood * Operating a kiln at higher temperatures does increase the potential of fire. At high temperatures a kiln should have truckload and thereby reduce cost borer, Asian longhorned beetle, kiln. But probably the most impor - some kind of sprinkler system installed. per cord. Dry firewood can be wood wasp, etc.—with still more tant factor in drying firewood faster transported further and at a lower certain to come over time) are is chamber temperature. This is Table 3. Heating System Temperatures, Estimated Chamber Temperatures and Drying Times. cost than green firewood. In the doing what they were designed to because water moves faster from the end, it is up to the individual fire - do, and when combined with mod - inside to the outside of firewood wood company to explain why the ern conveyances, spread nonnative when the temperature is higher, customer will get better-burning species at alarming rates into areas especially if the temperature is wood at better overall prices. with no natural defense mecha - above boiling point (~212°F). nisms. A simple Google search on In Table 2 you see the differ - Firewood Markets the term “firewood quarantine ences in drying times as the tem - The firewood industry serves a areas” currently yields 9,870 peratures go up. These drying great many markets. Let’s consider results, a stark testament to how times naturally assume that plenty the three biggest: widespread local, state, and federal of heat and air circulation was avail - • Heating: firewood purchased concern has developed into regula - able. In a normal firewood kiln you purely for heating buildings or sim - tory oversight. Consequently, it will have a heat-up time and a ilar spaces (Delivery: normally bulk would seem that the only relevant treatment/drying time. delivery or sometimes large unit question for those who would pre - Furthermore, when most people loads). fer to remain in the full-time fire - talk about the drying temperature • Ambience: firewood used for wood business would be: How will in a firewood kiln, they focus on campfires, fire pits, chimneys, fire - you position your firewood business the air entering the firewood places, etc. (Delivery: normally bundles, some large unit loads, and Loading DRYING TEMPURATURE some bulk delivery). Method 140 ° F 180 ° F 220 ° F • Gourmet: used for commercial cooking and high-end private cook - Random / 287 hours 87 hours 29 hours ing (Delivery: commercial, medium loose stacking to large unit loads and private by mail orders). Parallel stacking 226 hours 97 hours 34 hours Like it or not, the shift toward kiln-dried and heat-treated fire - Source: Kiln-Drying Time of Split Oak Firewood from Forest Products Laboratory wood in the marketplace seems (Research note FPL-RN-0254 – August 1987) more a question of “when” rather Table 2. Drying Times for Oak Firewood to 20% MC. than “if.” If, due to state and feder -

3 • Sawmill & Woodlot time if you want to dry from fresh- on the firewood used to heat the essence, the design was nothing Next Generation size of kiln is currently available in To our knowledge, this kiln does split to 20% moisture content. Of kiln; however, much of this should more than a modified lumber Firewood Kilns. (Future) the marketplace. not exist as of 2014. However, we course letting the firewood air dry be a “free” by-product of your fire - kiln—the same conventional design We believe that making firewood Regarding the midsize to large believe it will eventually be built during the warmer months can help wood splitting operation (off-cut, with added airflow and heating kilns too large will make them less firewood operations/companies, our by someone to supply the needs of reduce both the time needed in a crotch, nonmarketable biomass). capacity. Such modified lumber efficient and ensure longer drying experience suggests a kiln with the larger firewood companies. kiln as well as the overall cost of kilns tend to be on the larger size cycles. We also believe it would be, specifications below: heating the kiln, but for the purpose Choosing the Best Heat with 15+ cord capacity, which tends in a practical sense, better to have •Loading capacity of 12 cords. Getting Started of staying on point I will retain the Source to reflect a larger capital invest - three 6-cord firewood kilns versus •Operating at 250°F–270°F on sup - Are you currently operating a standard of fresh-split to 20% . The mixture of firewood kilns that ment/commitment. one 18-cord kiln, as multiple small ply side (210°F–220°F on exit side) processor and considering expand - The next main design parameter have sold has changed significantly. A different option that entered kilns provide a redundancy to pro - for two-day drying. ing into firewood drying for either is to install a heat system with Three to four years ago the majori - the marketplace was the modified, tect production. Be it maintenance •Short air circulation through fire - bulk or bundle delivery? The enough heating capacity to accom - ty of units sold were heated using insulated container/van bodies— issues or fires (yes, kilns of all wood (10 feet or less). smallest firewood kiln available on plish the drying in the time wood waste. As the natural gas cost typically using hot-water heating brands can catch fire), redundancy •Wood-waste heat using wood the market has a 5 to 6 cord capaci - desired. Before we can begin to has come down over the last two supplied from an outdoor stove. of kiln units clearly offers value to chips/mulch/sawdust/etc. with air- ty per load. There are “high” tem - understand the energy needed to years, we have seen a shift to more These insulated shipping contain - any operation built on delivering to-air heat exchanger (eliminating perature and “low” temperature kiln-dry and heat-treat firewood, gas-heated kilns. LP and natural ers had the lower price point so product with consistency. the need for steam and expensive designs, with high-temp systems we must first determine how much gas units now represent 60% to many smaller operators could afford Moreover, should a fire occur, it is maintenance). drying the firewood at approxi - water needs to be removed from 70% of the firewood kilns sold by them. These containers were not much easier to contain a 6-cord fire •Wood-waste storage for two to mately 260°F in two days or less, the firewood itself. my company, Kiln-direct. very efficient for multiple reasons than an 18-cord fire. As a final note, four days of operation. and low-temp systems drying the sprinkler systems should always be •Automatic wood ignition (no man - firewood utilizing hot water heat in considered on kilns, especially if ual start-up needed). five to seven days. In most cases, SPECIES Weight of Fresh-Split Weight at 20% MC Water to Be Removed using wood-waste-fired kilns. •Fire suppression system. you will also need firewood bas - Alder 3,604 lbs. 2,218 lbs. 1,386 lbs. We believe that the ideal size for •Delivered in one unit to be placed kets—preferably two sets—one set Ash, green 4,237 lbs. 3,178 lbs. 1,059 lbs. a small operation is around 5- to 6- on a flat, concrete slab to make in the kiln and one set getting cord capacity per kiln with a 2-day installation easy, keep investment processed and loaded with new Hackberry 4,039 lbs. 2,938 lbs. 1,101 lbs. drying process with either gas or down, and ensure kiln is consid - firewood to be dried. This is a Maple, soft 3,960 lbs. 2,640 lbs. 1,320 lbs. wood-waste heating. This type and ered a piece of equipment. major investment. Oak, red 4,886 lbs. 3,350 lbs. 1,536 lbs. Average water loss per cord needed to dry from fresh-split to 20%: 1,280 lbs. Source: www.engineeringtoolbox.com/weigt-wood-d_821.html Table 4. Water to Be Removed When Drying Firewood. How Many Pounds Are Removed to Dry Firewood?

Table 4 shows six different Basically, for the general fire - (low operating temperature and species and their fresh-split weight wood operation, the first choice poor air circulation, among others). versus their weight at 20% MC. would be natural gas heating, then Furthermore, as insulated shipping This shows that you need to wood waste, and then LP gas heat - containers were originally designed remove more than 1,270 pounds of ing. One of our customers has cho - for cold storage, the very hot and water per cord, on average, to reach sen wood waste heat even though humid conditions of a firewood kiln an average of 20% MC. With this that customer has access to natural led a relatively short kiln lifespan. much water to be removed, a lot of gas. Reason: They burn their tree energy will be required. This is service debris to fire the kiln Firewood Kilns Available why it often takes so long to dry instead of paying dumping fees for Today (Present) the firewood. their biomass. On the other hand, During the last five years, we have Table 5 notes the numbers for several firewood companies who seen the arrival of “true” firewood removing 1,270 pounds of water. have purchased our firewood kilns kilns with 6 to 15 cord capacity, The column for “Theoretical Lab have both wood waste heating kilns engineered to operate at high tem - Conditions” in Table 5 is basically and gas heating kilns. The “best” peratures (~250°F–270°F) for effi - the energy needed if there was heating system is an individual cient/quick cycle times, built with absolutely no energy wasted in the choice dependent upon what works well-insulated chambers, and offer - drying process. This is not opera - for your situation. ing multiple fuel options for heat - tionally possible due to transfer loss, ing—LP gas, natural gas, and wood venting, door seals, loss through Some Firewood Kiln waste. At present, approximately walls/roof, etc. The next column is History (Past) 2/3 of these are sold with gas heat - based on real firewood kiln experi - Kiln manufacturers initially utilized ing with the remaining 1/3 ences. As you read the table, it is existing lumber kiln design in the equipped for wood waste heating. worth noting that I have put a price hope of drying firewood. In

5 • Sawmill & Woodlot Nov/Dec 2014 • 6 GREEN SEASONED KILN-DRIED wood heat KILN-DRIED LP gas KILN-DRIED natural gas ENERGY COST FOR DRYING 1 CORD OF FIREWOOD THEORETICAL FIREWOOD KILN LAB CONDITIONS CONDITIONS Cost of one cord of firewood logs delivered Estimated weight of green firewood: 4,150 lbs./cord to your location 120 120 120 120 120 (oak=4,900 lbs., maple, soft=3,960 lbs., ash=4,240 lbs., Add 20% as total waste factor (10% for splitting + hackberry=4,040lbs., alder=3,600 lbs.) = average 4,150 lbs./cord 10% shrinkage when drying) 12 24 24 24 24 Estimated weight of dry firewood: 2,880 lbs./cord Cost of splitting firewood 35 35 35 35 35 (oak=3,425 lbs., maple, soft=2,640 lbs., ash=3,181lbs., Cost of drying firewood hackberry=2,940 lbs., alder=2,220 lbs.) = average 2,880 lbs./cord (or seasoning) including paying for equipment -- 15 50 80 40 Amount of water extracted per cord of firewood to be dried. 1,270 lbs./cord 1,270 lbs./cord Total cost per cord of firewood 167 194 229 259 219 How much energy will it take to evaporate 1 lb. of water? Sales price for a full cord 190 250 325 325 325 Starting temperature is 60° F. Revenue from 1,000 cord $190,000 $250,000 $325,000 $325,000 $325,000 Raising 1 lb. of water from 60° F to 212° F = 152 Btu (1Btu = 1° F per lb.). Evaporating 1 lb. of water at 212° F = 971 Btu. Theoretical energy Total cost to produce 1,000 cord $167,000 $194,000 $229,000 $259,000 $219,000 needed to evaporate 1 lb. of water from 60° F = 1,123 Btu. If there is a heat waste factor in any kiln, you will need much more Net estimated profit heat due to heat energy escaping during venting, or through walls, on 1,000 cord $23,000 $56,000 $96,000 $66,000 $106,000 floors, and other inefficiencies. Estimated profit margin 13.8% 22.4% 29.5% 20.3% 32.6% The rule of thumb in lumber drying is 35%–60% waste factor, which means Extra investment it will cost between 1,700 to 2,800 Btu to evaporate 1 lb. of water in a kiln. required to get going Extra inventory One 6 cord kiln + One 6 cord kiln + One 6 cord kiln + 2 sets of baskets 2 sets of baskets 2 sets of baskets How much energy does it take to evaporate 1,270 lbs. ~ $120,000 ~70,000 ~70,000 of water from firewood? 1.4 million Btu between 2.2 Theoretical: 1,270 lbs. of water x 1,123 Btu/lbs. = 1.4 million Btu (not possible). million Btu and This is a generic comparison based on speaking with several firewood producers. Your costs may vary, but this table should help you develop your own cost LOW Estimate: 1,270 lbs. of water x 1,700 Btu/lbs. = 2.2 million Btu. 3.6 million Btu calculation to help determine if kiln-drying firewood can be profitable for you and your business. The prices and cost we received from our customer varied HIGH Estimate: 1,270 lbs. of water x 2,800 Btu/lbs = 3.6 million Btu. greatly depending on the state and closeness to a metropolitan area. You must...... (author—missing sentence here?) Table 6. Costing and Profit Estimated for a 1,000 Cord Annual Production. How much energy does it take to raise 1 cord of firewood from approx. approx. 60° F to about 212° F? 440,000 Btu 600,000 Btu It is sound practice to consider times. Second, to dry 6 cords of areas, you can expect around $325 Average weight of firewood dry (with 20% water) = 2,880 lbs. the questions below in order to firewood to 20% MC will require to $375 per cord for thoroughly Temperature increase is (212° F - 60° F) = 152° F increase. Approximately 1 Btu/lbs./1° F increase. choose the best long-term firewood between 16.8 and 24 million Btu. kiln-dried firewood picked up at Total energy needed to raise wood temperature kiln: At 250,000 Btu/hour, a heating sys - your yard. For bundles of thorough - (2,880 lbs. x 152 Btu/lbs.) = 437,760 Btu. •How many cords do you need to tem with 80% efficiency creates ly dried and heat-treated firewood, dry in a certain period? approximately 200,000 Btu/hour— the average rate seems to be some - Total energy consumption needed to dry 1 cord of firewood: •How many cords do you want to suggesting a drying time of 84 to where between $2.25 and $3 per THEORETICAL: (1,400,000 + 440,000) Btu = 1.8 million Btu heat-treat/dry per charge? 120 hours. Visit several of the refer - bundle picked up at your facility. LOW estimate: (2,200,000 + 600,000) Btu = 2.8 million Btu •Do you need to heat-treat and to ences provided by the kiln compa - Please see Table 6 for a generic HIGH estimate: (3,600,000 + 600,000) Btu = 4.2 million Btu what standard? ny, making sure the company you overview of firewood economics. Total cost in energy to dry one cord of wood in the 1.8 million Btu 2.8 million Btu •What fuel do you want to use (gas, are visiting is more than four to six Furthermore, you can literally log MINIQUICK Firewood Kiln to 4.2 million Btu wood waste, or something else)? hours away so they are not future on Monday, split on Tuesday, kiln- •How dry do you want your fire - competitors. You will find distant dry on Wednesday to Thursday, Estimated cost of energy with wood waste: ~10% of a cord 16%–24% of a cord wood to be? operations more open to sharing and then deliver on Friday. This 1 cord of firewood is normally 15–20 million Btu up to $10 $16 –$24 Begin by talking with companies information, as they are not threat - approach would mean you have (cost per cord = $0–$100) that sell firewood kilns. Be sure ened by you as a competitor. reached three standards unobtain - you get several references and ask During your visit, ask for a few fire - able by traditional seasoning: con - Estimated cost of energy using LP ga:s $40 $62–$92 pointed questions. If a company wood samples that have recently sistent moisture content, you have Each gallon of LP gas = 91,000 Btu /gal. LP gas Current gas costs: $2 per gal. (probably too low) promises three-day cycle times come out of the kiln so you can test satisfied heat treatment require - THEORETICAL: 1,800,000 / 91,000 Btu/gal. = about 20 gal. with a maximum temperature of moisture content later. Better yet, if ments and provided consistent pro - LOW estimate: 2,800,000 / 91,000 Btu/gal. = about 31 gal. 180°F chamber temperature in a 6- possible, try to have a look at the duction. HIGH estimate: 4,200,000 / 91,000 Btu/gal. = about 46 gal. cord kiln with a 250,000-Btu hot records from a regular run to make water stove, then there is good rea - sure the kiln can actually reach the How Might New Heat Estimated cost of energy using natural gas: $14.40 $22–$33 son to be suspicious. First, 180°F is temperatures that the salespeople 1 cu. ft. of natural gas = 1,000 Btu (100 cu. ft. = 1 therm) Treating and Drying Current average cost for 1 therm of natural gas = $0.80 per therm the supply temp (meaning the are promising. They may refuse, Standards Influence the hottest temperature in the kiln); but it is worth the asking. Theoretical: 1,800,000 / 100,000 Btu/therm – about 18 therm THIS CALCULATION ASSUMES THE FIREWOOD IS DRIED Industry? Low estimate: 2,800,000 / 100,000 Btu/therm – about 28 therm TO 20% AVERAGE MOISTURE CONTENT—MUCH OF the exit temperature will be signifi - Most importantly, before invest - It used to be that all a person need - High estimate: 4,200,000 / 100,000 Btu/therm – about 42 therm THE KILN- DRIED FIREWOOD ON THE MARKET TODAY cantly lower (15°F or more). If this ing in a kiln, be sure you can make ed to start a firewood business was DOES NOT, IN FACT, MEET THIS STANDARD. is the case, then the numbers can - a profit. If you are within three to a splitter, chain saw, and a pickup Table 5. Energy and Cost of Drying Firewood. not be reconciled to Table 2 drying four hours of major metropolitan truck. This model seems to have

7 • Sawmill & Woodlot Nov/Dec 2014 • 8 DRYING FIREWOOD created many “low bidders” in the marketplace and often disturbs genuine full-time operations because their infrastructure costs prohibit them from matching the unsustainable low price offered by the fellow who cuts for “beer money.” Heat treating and kiln drying has separated the full-time firewood pro - ducers from the “hobbyists.” The current firewood regulations do not really stop the “nickel and dime” producers, as most of these deliver close to home. However, it does require a substantial investment to move from hobbyist to full-time pro - duction, probably in the realm of $200,000 to $400,000 to cover a big - ger processor, firewood kiln, skid- steer, inventory, and working capital. Practically speaking, once people go full-time they need to produce a minimum of 500 to 1,000 cords annu - ally to make a profit. Realistically, the long-term volume to stay in busi - ness is more likely above 2,000 cords annually. In the end, to be a full-time firewood operation, you likely end up with a mixture of local bulk deliv - ery at lower prices and more prof - itable kiln-dried firewood in bundles and/or bulk delivery. The nature of the firewood industry has changed. A clear divi - sion between hobbyists and full- time firewood producers has been a healthy development for the indus - try, and the establishment of addi - tional small to midsize operations (2,000–5,000 cords annually) has stimulated improved operational efficiencies for smaller-scale opera - tions through innovation. •

Niels Jorgensen started Kiln-direct in 1994 by selling lumber kiln compo - nents. Kiln-direct matured as the demand for pallet kilns grew and it became one of the primary suppliers to the pallet industry. Kiln-direct later diversified into small to midsize lumber kilns and more recently into firewood kilns specifically designed for drying and heat-treating firewood.

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